Feedforward amplifier

ABSTRACT

A feedforward amplifier includes a first power splitter for dividing an input signal into two paths. The first path, in sequence, includes a first vector adjuster, a main amplifier, a second power splitter and a delay circuit. The second path, in sequence, includes a delay circuit, a distortion detecting power combiner, a second vector adjuster and an error amplifier. The distortion detecting power combiner combines a portion of a signal from the first path with a signal in the second path. Each vector adjuster adjusts amplitude and phase of a signal in each path. A distortion suppression power combiner synthesizes a signal in the first path with a signal in the second path. Control is included for stopping operation of the error amplifier or main amplifier based on a predetermined condition.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a feedforward amplifier and acommunication equipment, which are primarily used for a base stationdevice of mobile communication equipment.

[0003] 2. Related Art of the Invention

[0004] In recent years, a high-output linear power-amplifier,compensated for distortion by a feedforward method, has been used for abase station device of mobile communication equipment.

[0005]FIG. 12 shows an example of the configuration of a conventionalfeedforward amplifier. In FIG. 12, reference numeral 1 denotes an inputterminal, 2 an output terminal, 3 and 8 power splitters, 4 and 9power-combiners, 5 and 13 vector adjustors, 6 a main amplifier, 7 and 10delay circuits, and 14 an error amplifier, respectively. Further,symbols a to k and m added to the power splitters 3 and 8 and thepower-combiners 4 and 9 show respective ports.

[0006] Hereinafter, the operation of the feedforward amplifierconfigured as described above will be described.

[0007] First, an input signal input from the input terminal 1 andincluding a plurality of carrier frequency components is split into twoparts by the power splitter 3, and the two parts are output from theport b and port c respectively. The signal output from the port b isamplified by the main amplifier 6 through the vector adjustor 5, andthen passes through the power splitter 8 and the delay circuit 10,inputting into the port j of the power-combiner 4. At this time, thesignal including distortion components caused by intermodulation due tonon-linearity of the main amplifier 6 in addition to the carrierfrequency components are input into the port j.

[0008] Further, part of the output signal of the main amplifier 6 istook out from a port f of the power splitter 8 and input into a port hof the power-combiner 9. On the other hand, the signal output from theport c inputs into a port g of the power-combiner 9 through the delaycircuit 7. Here, the vector adjustor 5 and delay circuit 7 are adjustedsuch that the carrier frequency components of the respective signalsinput into the port g and the port h may have the same amplitudes andopposite phases, thereby a signal having only the distortion componentswith the carrier frequency components canceled out being output from theport i.

[0009] Next, the signal output from the port i is amplified by the erroramplifier 14 through the vector adjustor 13 and inputs into a port k ofthe power-combiner 4. Here, the vector adjustor 13 and the delay circuit10 are adjusted such that the distortion components of signals inputinto the port j and port k may have the same amplitudes and oppositephases, thereby a signal having only the carrier frequency componentswith the distortion components canceled out being output from a port mof the power-combiner 4 to the output terminal 2.

[0010] FIGS. 13(a) to (d) shows frequency spectra of signals at theports a, d, i and m.

[0011] As shown in FIG. 13(a), the frequency spectrum of the signal atthe port a is composed of carrier frequency components. Also, as shownin FIG. 13(b), the frequency spectrum of the signal at the port d iscomposed of carrier frequency components and distortion components.Further, as shown in FIG. 13(c), the frequency spectrum of the signal atthe port i is composed of only the distortion components with thecarrier frequency components canceled out. Further, as shown in FIG.13(d), the frequency spectrum of the signal from the port m is composedof only the carrier frequency components with the distortion componentscanceled out.

[0012] However, the configuration of FIG. 12 has a problem that adecrease in output power leads to a decrease in efficiency as shown inFIG. 14. Here, the efficiency means the ratio of output power toconsumption power.

[0013] Further, in a base station device and the like of mobilecommunication equipment that uses the configuration of FIG. 12, there isa problem that when the main amplifier fails, the device can not workand thus the communication stops completely.

SUMMARY OF THE INVENTION

[0014] Considering the above problems, the invention has an object toprovide a feedforward amplifier and a communication equipment of whichefficiency does not decrease even in the event of the reduction ofoutput power.

[0015] Further, the invention has another object to provide afeedforward amplifier and a communication equipment of whichcommunication does not stop completely even in the event of the failureof the main amplifier.

[0016] The 1st invention of the present invention is a feedforwardamplifier comprising:

[0017] a first power splitter for splitting an input signal into twoparts;

[0018] a first vector adjustor for adjusting the amplitude and phase ofone output signal of said first power splitter;

[0019] a main amplifier for amplifying an output signal of said firstvector adjustor;

[0020] a second power splitter for splitting an output signal of saidmain amplifier into two parts;

[0021] a first delay circuit for delaying the other output signal ofsaid first power splitter;

[0022] a distortion detection power-combiner for synthesizing one outputsignal of said second power splitter and an output signal of said firstdelay circuit;

[0023] a second delay circuit for delaying the other output signal ofsaid second power splitter;

[0024] a second vector adjustor for adjusting the amplitude and phase ofthe output signal of said distortion detection power-combiner;

[0025] an error amplifier for amplifying the output signal of saidsecond vector adjustor;

[0026] a distortion suppression power-combiner for synthesizing theoutput signal of said second delay circuit and the output signal of saiderror amplifier; and

[0027] control means of at least stopping the operation of said erroramplifier or said main amplifier depending on a predetermined condition.

[0028] The 2nd invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0029] first signal level detection means of detecting a first signallevel that is the signal level of said input signal or the signal levelof a baseband signal in a baseband signal generating portion, or thesignal level of a transmitting signal in a transmitting circuit,

[0030] wherein said predetermined condition represents said first signallevel, and

[0031] when said detected first signal level is not higher than apredetermined value, said control means stops the operation of saiderror amplifier.

[0032] The 3rd invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0033] first signal level detection means of detecting a first signallevel that is the signal level of a received signal in a receivingcircuit,

[0034] wherein said predetermined condition represents said first signallevel, and

[0035] when said detected first signal level is not lower than apredetermined value, said control means stops the operation of saiderror amplifier.

[0036] The 4th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0037] first signal level detection means of detecting a first signallevel that is the signal level of said input signal, or the signal levelof a baseband signal in a baseband signal generating portion, or thesignal level of a transmitting signal in a transmitting circuit, or thesignal level of a received signal in a receiving circuit; and

[0038] second signal level detection means of detecting a second signallevel that is the signal level of said output signal,

[0039] wherein said predetermined condition represents gain of saidsecond signal level to said first signal level, and

[0040] when said gain is out of a predetermined value, said controlmeans stops the operation of said main amplifier.

[0041] The 5th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0042] first signal level detection means of detecting a first signallevel that is the signal level of an input signal, or the signal levelof a baseband signal in a baseband signal generating portion, or thesignal level of a transmitting signal in a transmitting circuit,

[0043] wherein said predetermined condition represents said first signallevel, and

[0044] when said first signal level is not higher than a predeterminedvalue, said control means stops the operation of said main amplifier.

[0045] The 6th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0046] first signal level detection means of detecting a first signallevel that is the signal level of a received signal in a receivingcircuit,

[0047] wherein said predetermined condition represents said first signallevel, and

[0048] when said first signal level is not lower than a predeterminedvalue, said control means stops the operation of said main amplifier.

[0049] The 7th invention of the present invention is the feedforwardamplifier according to 4th or 5th inventions, wherein said distortionsuppression power-combiner is a variable power-combiner that can have atight coupling state and a loose coupling state, and

[0050] when said first signal level is higher than a predeterminedvalue, said control means controls said variable power-combiner to havesaid loose coupling state, and

[0051] when said first signal level is not higher than the predeterminedvalue, said control means controls said variable power-combiner to havesaid tight coupling state.

[0052] The 8th invention of the present invention is the feedforwardamplifier according to 4th or 6th inventions, wherein said distortionsuppression power-combiner is a variable power-combiner that can have atight coupling state and a loose coupling state,

[0053] when said first signal level is lower than a predetermined value,said control means controls said variable power-combiner to have saidloose coupling state, and

[0054] when said first signal level is not lower than the predeterminedvalue, said control means controls said variable power-combiner to havesaid tight coupling state.

[0055] The 9th invention of the present invention is the feedforwardamplifier according to 4th or 5th inventions, wherein, when said firstsignal level is not higher than a predetermined value, said controlmeans performs such control that the output signal of said erroramplifier can be output without passing through said distortionsuppression power-combiner.

[0056] The 10th invention of the present invention is the feedforwardamplifier according to 4th or 6th inventions, wherein, when said firstsignal level is not lower than a predetermined value, said control meansperforms such control that the output signal of said error amplifier canbe output without passing through said distortion suppressionpower-combiner.

[0057] The 11th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0058] first signal level detection means of detecting a first signallevel that is the signal level of an input signal, or the signal levelof a baseband signal in a baseband signal generating portion, or thesignal level of a transmitting signal in a transmitting circuit,

[0059] wherein said predetermined condition represents said first signallevel, and

[0060] when said first signal level is not higher than a firstpredetermined value and higher than a second predetermined value that issmaller than said first predetermined value, said control means stopsthe operation of said error amplifier, and when said first signal levelis not higher than said second predetermined value, said control meansstops the operation of said main amplifier.

[0061] The 12th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0062] first signal level detection means of detecting a first signallevel that is the signal level of a received signal in a receivingcircuit,

[0063] wherein said predetermined condition represents said first signallevel, and

[0064] when said first signal level is not higher than a firstpredetermined value and higher than a second predetermined value that issmaller than said first predetermined value, said control means stopsthe operation of said error amplifier, and when said first signal levelis not lower than said first predetermined value, said control meansstops the operation of said main amplifier.

[0065] The 13th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0066] a third power splitter for splitting the output signal of saiderror amplifier into two parts;

[0067] a third delay circuit for delaying one output signal of saidthird power splitter;

[0068] a fourth power splatter for splitting the output signal of saiddistortion suppression power-combiner into two parts;

[0069] a fourth delay circuit for delaying one output signal of saidfourth power splitter;

[0070] a second distortion detection power-combiner for synthesizing theoutput signal of said fourth delay circuit and the other output signalof said third power splitter;

[0071] a third vector adjustor for adjusting the amplitude and phase ofthe output signal of said second distortion detection power-combiner;

[0072] a second error amplifier for amplifying the output signal of saidthird vector adjustor;

[0073] a second distortion suppression power-combiner for synthesizingthe output signal of said third delay circuit and the output signal ofsaid second error amplifier; and

[0074] first signal level detection means of detecting a first signallevel that is the signal level of said input signal, or the signal levelof a baseband signal in a baseband signal generating portion, or thesignal of a transmitting signal in a transmitting circuit,

[0075] wherein said control means also stops the operation of saidsecond error amplifier depending on said predetermined condition,

[0076] said predetermined condition represents said first signal level,and

[0077] when said first signal level is higher than a predeterminedvalue, said control means stops the operation of said second erroramplifier and performs such control that the output signal of said erroramplifier can not be input by said third power splitter, and performssuch control that the output signal of said distortion suppressionpower-combiner can be output to the outside, and

[0078] when said first signal level is not higher than the predeterminedvalue, said control means stops the operation of said main amplifier andperforms such control that the output signal of said error amplifier cannot be input by said distortion suppression power-combiner but can beinput by said third power splitter, and performs such control that theoutput signal of said second distortion suppression power-combiner canbe output to the outside.

[0079] The 14th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0080] a third power splitter for splitting the output signal of saiderror amplifier into two parts;

[0081] a third delay circuit for delaying one output signal of saidthird power splitter;

[0082] a fourth power splitter for splitting the output signal of saiddistortion suppression power-combiner into two parts;

[0083] a fourth delay circuit for delaying one output signal of saidfourth power splitter;

[0084] a second distortion detection power-combiner for synthesizing theoutput signal of said fourth delay circuit and the other output signalof said third power splitter;

[0085] a third vector adjustor for adjusting the amplitude and phase ofthe output signal of said second distortion detection power-combiner;

[0086] a second error amplifier for amplifying the output signal of saidthird vector adjustor;

[0087] a second distortion suppression power-combiner for synthesizingthe output signal of said third delay circuit and the output signal ofsaid second error amplifier; and

[0088] first signal level detection means of detecting a first signallevel that is the signal level of a received signal in a receivingcircuit,

[0089] wherein said control means also stops the operation of saidsecond error amplifier depending on said predetermined condition,

[0090] said predetermined condition represents said first signal level,and

[0091] when said first signal level is lower than a predetermined value,said control means stops the operation of said second error amplifierand performs such control that the output signal of said error amplifiercan not be input by said third power splitter, and performs such controlthat the output signal of said distortion suppression power-combiner canbe output to the outside, and

[0092] when said first signal level is not lower than the predeterminedvalue, said control means stops the operation of said main amplifier andperforms such control that the output signal of said error amplifier cannot be input by said distortion suppression power-combiner but can beinput by said third power splitter, and performs such control that theoutput signal of said second distortion suppression power-combiner canbe output to the outside.

[0093] The 15th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0094] a third power splitter for splitting the output signal of saiderror amplifier into two parts;

[0095] a third delay circuit for delaying one output signal of saidthird power splitter;

[0096] a fourth power splitter for splitting the output signal of saiddistortion suppression power-combiner into two parts;

[0097] a fourth delay circuit for delaying one output signal of saidfourth power splitter;

[0098] a second distortion detection power-combiner for synthesizing theoutput signal of said fourth delay circuit and the other output signalof said third power splitter;

[0099] a third vector adjustor for adjusting the amplitude and phase ofthe output signal of said second distortion detection power-combiner;

[0100] a second error amplifier for amplifying the output signal of saidthird vector adjustor;

[0101] a second distortion suppression power-combiner for synthesizingthe output signal of said third delay circuit and the output signal ofsaid second error amplifier; and

[0102] first signal level detection means of detecting a first signallevel that is the signal level of said input signal, or the signal levelof a baseband signal in a baseband signal generating portion, or thesignal of a transmitting signal in a transmitting circuit,

[0103] wherein said control means also stops the operation of saidsecond error amplifier depending on said predetermined condition,

[0104] said predetermined condition represents said first signal level,and

[0105] when said first signal level is higher than a predeterminedvalue, said control means stops the operation of said second erroramplifier and performs such control that the output signal of said erroramplifier can not be input by said third power splitter, and performssuch control that the output signal of said distortion suppressionpower-combiner can be output to the outside, and

[0106] when said first signal level is not higher than the firstpredetermined value and higher than a second predetermined value that issmaller than said first predetermined value, said control means stopsthe operation of said main amplifier and performs such control that theoutput signal of said error amplifier can not be input by saiddistortion suppression power-combiner but can be input by said thirdpower splitter, and performs such control that the output signal of saidsecond distortion suppression power-combiner can be output to theoutside, and

[0107] when said first signal level is not higher than the secondpredetermined value, said control means stops the operation of saiderror amplifier and stops the operation of said second error amplifier,and performs such control that the output signal of said distortionsuppression power-combiner can be output to the outside.

[0108] The 16th invention of the present invention is the feedforwardamplifier according to 1st invention, further comprising:

[0109] a third power splitter for splitting the output signal of saiderror amplifier into two parts;

[0110] a third delay circuit for delaying one output signal of saidthird power splitter;

[0111] a fourth power splitter for splitting the output signal of saiddistortion suppression power-combiner into two parts;

[0112] a fourth delay circuit for delaying one output signal of saidfourth power splitter;

[0113] a second distortion detection power-combiner for synthesizing theoutput signal of said fourth delay circuit and the other output signalof said third power splitter;

[0114] a third vector adjustor for adjusting the amplitude and phase ofthe output signal of said second distortion detection power-combiner;

[0115] a second error amplifier for amplifying the output signal of saidthird vector adjustor;

[0116] a second distortion suppression power-combiner for synthesizingthe output signal of said third delay circuit and the output signal ofsaid second error amplifier; and

[0117] first signal level detection means of detecting a first signallevel that is the signal level of a received signal in a receivingcircuit,

[0118] wherein said control means also stops the operation of saidsecond error amplifier depending on said predetermined condition,

[0119] said predetermined condition represents said first signal level,and

[0120] when said first signal level is lower than a second predeterminedvalue, said control means stops the operation of said second erroramplifier and performs such control that the output signal of said erroramplifier can not be input by said third power splitter, and performssuch control that the output signal of said distortion suppressionpower-combiner can be output to the outside, and

[0121] when said first signal level is not higher than a firstpredetermined value that is larger than said second predetermined valueand higher than said second predetermined value, said control meansstops the operation of said main amplifier and performs such controlthat the output signal of said error amplifier can not be input by saiddistortion suppression power-combiner but can be input by said thirdpower splitter, and performs such control that the output signal of saidsecond distortion suppression power-combiner can be output to theoutside, and

[0122] when said first signal level is not lower than the firstpredetermined value, said control means stops the operation of saiderror amplifier and stops the operation of said second error amplifier,and performs such control that the output signal of said distortionsuppression power-combiner can be output to the outside.

[0123] The 17th invention of the present invention is the feedforwardamplifier according to any one of 2nd, 4th, 5th, 11th, 13th, and 15thinventions; wherein said first signal level detection means is providedin an upstream stage of said first power splitter, or between said firstpower splitter and said first vector adjustor, or between said firstvector adjustor and said main amplifier, or between said first powersplitter and said first delay circuit, or between said first delaycircuit and said distortion detection power-combiner, or at the input ofsaid baseband signal generating portion, or at the output of saidbaseband signal generating portion, or in said baseband signalgenerating potion, or at the input of said transmitting circuit, or atthe output of said transmitting circuit, or in said transmittingcircuit.

[0124] The 18th invention of the present invention is the feedbackamplifier according to any one of 3rd, 4th, 6th, 12th, 14th, and 16thinventions, wherein said first signal level detection means is providedat the input of said receiving circuit, or at the output of saidreceiving circuit, or in said receiving circuit.

[0125] The 19th invention of the present invention is the feedforwardamplifier according to 4th invention, wherein said second signal leveldetection means is provided in a downstream stage of said distortionsuppression power-combiner, or between said second power splitter andsaid second delay circuit, or between said second delay circuit and saiddistortion suppression power-combiner.

[0126] The 20th invention of the present invention is the feedforwardamplifier according to 17th invention,

[0127] wherein said first signal level is the signal level of said inputsignal, and when said first signal level detection means detects thesignal level of said input signal,

[0128] said first signal level detection means has a signal leveldetection power-splitter for splitting said input signal into two partsand detection means of detecting said signal level of one output signalof said signal level detection power-splitter, and

[0129] the other output signal of said signal level detection powersplitter is supplied to a downstream stage.

[0130] The 21st invention of the present invention is the feedforwardamplifier according to 19th invention, wherein said second signal leveldetection means has a signal level detection power-splitter forsplitting said output signal into two parts and detection means ofdetecting said signal level of one output signal of said signal leveldetection power-splitter, and

[0131] the other output signal of said signal level detectionpower-splitter is supplied to a downstream stage.

[0132] The 22nd invention of the present invention is the feedforwardamplifier according to any one of 2nd, 3rd, 11th, 12th, 15th, and 16thinventions, wherein the stopping of the operation of said erroramplifier is to perform such control that the power supply for saiderror amplifier can be turned off and/or to perform such control thatthe output signal of said second vector adjustor can not be input bysaid error amplifier.

[0133] The 23rd invention of the present invention is the feedforwardamplifier according to any one of 4th, 5th, 6th, 11th, 12th, 13th, 14th,15th, and 16th inventions, wherein the stopping of the operation of saidmain amplifier is to perform such control that the power supply for saidmain amplifier can be turned off and/or to perform such control that theoutput signal of said first vector adjustor can not be input by saidmain amplifier.

[0134] The 24th invention of the present invention is the feedforwardamplifier according to any one of 13th, 14th, 15th, and 16th inventions,wherein the stopping of the operation of said second error amplifier isto perform such control that the power supply for said second erroramplifier can be turned off and/or to perform such control that theoutput signal of said third vector adjustor can not be input by saidsecondary error amplifier.

[0135] The 25th invention of the present invention is a communicationequipment comprising:

[0136] a baseband generating portion for generating a baseband signal;and

[0137] a transmitting circuit for outputting a transmitting signal fromsaid baseband signal generated, wherein the feedforward amplifieraccording to any one of 1st to 6th, 11th to 16th, 19th, and 21stinventions is used for said transmitting circuit.

[0138] In the feedforward amplifier according to the invention, becausethe level of distortion caused by the main amplifier is low at lowoutput power, output signals of the main amplifier are then output as-isfrom the output terminal of the distortion suppression power-combiner,and further the power source of the error amplifier is turned off toallow the high efficiency of the feedforward amplifier.

[0139] Further, when an abnormal event occurs in the main amplifier, theerror amplifier can be used to amplify and output the input signal,thereby allowing the improved reliability of the feedforward amplifier.

[0140] Furthermore, equipping communication equipments such as mobilecommunication equipments with the feedforward amplifier according to theinvention allows the higher efficiency and improved reliability ofcommunication equipments such as mobile communication equipments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0141]FIG. 1 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 1.

[0142]FIG. 2 shows a characteristic diagram of distortion versus outputpower of a main amplifier.

[0143]FIG. 3 shows a characteristic diagram of efficiency versus outputpower of the feedforward amplifier according to the embodiment 1 of theinvention.

[0144]FIG. 4 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 2 of the invention.

[0145]FIG. 5 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 3 of the invention.

[0146]FIG. 6 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 4 of the invention.

[0147]FIG. 7 shows a configuration diagram of the feedforward amplifieraccording to embodiment 5 of the invention.

[0148]FIG. 8 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 6 of the invention.

[0149]FIG. 9 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 7 of the invention.

[0150]FIG. 10 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 8 of the invention.

[0151]FIG. 11 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 9 of the invention.

[0152]FIG. 12 shows a configuration diagram of a conventionalfeedforward amplifier.

[0153]FIG. 13 shows a frequency spectrum of signals at the ports a, d,i, and m of FIG. 12.

[0154]FIG. 14 shows a characteristic diagram of efficiency versus outputpower of a conventional feedforward amplifier.

[0155] Description of Symbols

[0156]1 . . . Input terminal

[0157]2 . . . Output terminal

[0158]3, 8, 16, 26, 31, 36 . . . Power splitter

[0159]4, 9, 32, 37 . . . Power-combiner

[0160]5, 13, 39 . . . Vector adjustor

[0161]6 . . . Main amplifier

[0162]7, 10, 35, 38 . . . Delay circuit

[0163]11, 21, 24, 25, 33 . . . Switch circuit

[0164]12, 22, 34 . . . Terminating resistor

[0165]14 . . . Error amplifier

[0166]15 . . . Error amplifier power switch circuit

[0167]17, 27 . . . Signal level detection circuit

[0168]18 . . . Control circuit

[0169]19, 29 . . . Signal level detection portion

[0170]20 . . . Variable power-combiner

[0171]23 . . . Main amplifier power-switch-circuit

[0172]40 . . . Power amplifier

[0173]41 . . . Power amplifier power switch circuit

[0174]42 . . . First feedforward amplifier circuit

[0175]43 . . . Second feedforward amplifier circuit

PREFERRED EMBODIMENTS OF THE INVENTION

[0176] Hereinafter, the embodiments of the invention will be describedwith reference to the drawings.

[0177] Here, the same components as the conventional feedforwardamplifier of FIG. 12 are denoted by the same symbols.

[0178] (Embodiment 1)

[0179]FIG. 1 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 1 of the invention. In FIG. 1, referencenumeral 11 denotes a switch circuit, 12 a terminating resistor, 15 anerror amplifier power switch, 16 a power splitter, 17 a signal leveldetection circuit, and 18 a control circuit for switching the switchcircuit 11 and the error amplifier power switch circuit 15 depending onthe signal level detected by the signal level detection circuit 17,respectively. The power splitter 16 and the signal level detectioncircuit 17 constitute a signal level detection portion 19. Further, asymbol n added to the power splitter 16 shows a port.

[0180] By the way, the power splitter 3 of the present embodiment is anexample of the first power splitter of the invention, the vectoradjustor 5 an example of the first vector adjustor, the power splitter 8an example of the second power splitter, the delay circuit 7 an exampleof the first delay circuit, the power-combiner 9 an example of thedistortion detection power-combiner, the delay circuit 10 an example ofthe second delay circuit, the vector adjustor 13 an example of thesecond vector adjustor, the power-combiner 4 an example of thedistortion suppression power-combiner, the control circuit 18 an exampleof the control means, and the signal level detection portion 19 anexample of the first signal level detection means, respectively.

[0181] For the feedforward amplifier configured as described above,hereinafter, its operation will be described with reference to thedrawings.

[0182] An input signal input from an input terminal 1 and including aplurality of carrier frequency components is input into a port a of thepower splitter 3 through the power splitter 16. Then, part of the inputsignal is took out from the port n of the power splitter 16 and inputinto the signal level detection circuit 17. The signal input into theport a of the power splitter 3 is split into two parts, which are outputthrough a port b and port c respectively.

[0183] The signal output from the port b is amplified by the mainamplifier 6 through the vector adjustor 5 and then input into a port jof the power-combiner 4 through the power splitter 8 and the delaycircuit 10. At this time, signals including distortion components causedby intermodulation due to the non-linearity of the main amplifier 6 inaddition to the carrier frequency components are input into the port j.

[0184] Further, part of the output signal of the main amplifier 6 istook out from a port f of the power splitter 8 and input into a port hof the power-combiner 9. On the other hand, the signal output from theport c is input into a port g of the power-combiner 9 through the delaycircuit 7.

[0185] Here, the vector adjustor 5 and the delay circuit 7 are adjustedsuch that the carrier frequency components of the signals input into theport g and the port h may have the same amplitudes and opposite phases,thereby a signal having only the distortion components with the carrierfrequency components canceled out being output from the port i.

[0186] Then, the signal output from the port i is input into a commonterminal 11 a of the switch circuit 11. Here, when the input signallevel detected by the signal level detection circuit 17 is higher thanP1 (dBm), the control circuit 18 connects the common terminal 11 a to anoutput switching terminal 11 b of the switch circuit 11, and furtherturns on the error amplifier power switch circuit 15. On the other hand,when the input signal level is not higher than P1 (dBm), the controlcircuit 18 connects the common terminal 11 a to an output switchingterminal 11 c of the switch circuit 11 and further turns off the erroramplifier power switch circuit 15.

[0187] First, when the input signal level is higher than P1 (dBm), thesignal input into the common terminal 11 a of the switch circuit 11 isamplified by the error amplifier 14 through the output switchingterminal 11 b and the vector adjustor 13, and then input into a port kof the power-combiner 4. Here, the vector adjustor 13 and the delaycircuit 10 are adjusted such that the distortion components of thesignals input into the port j and the port k may have the sameamplitudes and opposite phases, thereby a signal having only the carrierfrequency components with the distortion components canceled out beingoutput from a port m of the power-combiner 4 into an output terminal 2.

[0188] On the other hands when the input signal level is not higher thanP1 (dBm), the signal input into the common terminal 11 a of the switchcircuit 11 is absorbed by a terminating resistor 12 through the outputswitching terminal 11 c. For this reason, no signal is input into theport k of the power-combiner 4, and the signal input into the port j ofthe power-combiner 4 is output as-is from the port m to the outputterminal 2. That is, the output signal of the main amplifier 6 is outputas-is from the output terminal 2.

[0189] Generally, the level of distortions caused by the main amplifier6 decreases as its output power decreases as shown in FIG. 2. When thelevel of distortions included in the output signals of the mainamplifier 6 is not higher than D1 (e.g. −60 dBc) (wherein the inputsignal level corresponds to P1 (dBm)), it is no problem to output theas-is output signal of the main amplifier 6 to the output terminal 2. Atthis time, because the error amplifier power switch circuit 15 is turnedoff, the power consumed by the error amplifier 14 becomes zero,therefore allowing improvement of the efficiency at low output power asshown in FIG. 3.

[0190] By the way, in the above embodiment, although the input signallevel is used to switch the switch circuit 11 and the error amplifierpower switch circuit 15, it is apparent that the same operation can bealso obtained by switching them depending on the level of signals outputfrom the port b of the power splitter 3, the vector adjustor 5, the portf of the power splitter 8, the port c of the power splitter 3, or thedelay circuit 7. In this case, the signal level detection portion 19should be inserted in the position for the signal level to be detected.

[0191] (Embodiment 2)

[0192]FIG. 4 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 2 of the invention. In FIG. 4, referencenumeral 21 denotes a switch circuit, 22 a terminating resistor, 23 amain amplifier power-switch-circuit, 26 a power splitter, and 27 asignal level detection circuit, respectively. The power splitter 26 andthe signal level detection circuit 27 constitute a signal leveldetection portion 29.

[0193] The control circuit 18 switches the switch circuit 21 and themain amplifier power-switch-circuit 23 and adjusts the vector adjustor13, depending on the signal level detected by the signal level detectioncircuits 17 and 27.

[0194] By the way, the power splitter 3 of the present embodiment is anexample of the first power splitter of the invention, the vectoradjustor 5 an example of the first vector adjustor, the power splitter 8an example of the second power splitter, the delay circuit 7 an exampleof the first delay circuit, the power-combiner 9 an example of thedistortion detection power-combiner, the delay circuit 10 an example ofthe second delay circuit, the vector adjustor 13 an example of thesecond vector adjustor, the power-combiner 4 an example of thedistortion suppression power-combiner, the control circuit 18 an exampleof the control means, the signal level detection portion 19 an exampleof the first signal level detection means, and the signal leveldetection portion 29 an example of the second signal detection means,respectively.

[0195] With feedforward amplifier configured as described above, itsoperation will be described with reference to the drawing.

[0196] The embodiment 2 according to of the invention provides afeedforward amplifier in which, when an abnormal event occurs in themain amplifier 6; the error amplifier 14 directly amplifies inputsignals for outputting. When the main amplifier 6 normally operates, adifference between the output signal level detected by the signal leveldetection portion 29 and the input signal level detected by the signallevel detection portion 19 (the gain of the feedforward amplifier) iskept constant. However, the signal level difference between the outputsignal and the input signal is out of the constant value, the mainamplifier is then judged to be abnormal.

[0197] When the main amplifier 6 operates normally, the control circuit18 directly connects a common terminal 21 a to an output switchingterminal 21 b of the switch circuit 21 and also turns on the mainamplifier power-switch-circuit 23. At this time, the feedforwardamplifier according to the embodiment 2 of the invention performs thesame operation as conventional feedforward amplifiers.

[0198] On the other hand, when an abnormal event occurs in the mainamplifier 6, the control circuit 18 connects the common terminal 21 a toan output switching terminal 21 c of the switch circuit 21 and turns offthe main amplifier power-switch-circuit 23.

[0199] At this time, an input signal input from the input terminal 1 andincluding a plurality of carrier frequency components is split into twoparts by the power splitter 3 through the power splitter 16 and the twoparts are output from the port b and port c respectively. The signaloutput from the port b is absorbed by the terminating resistor 22.Further, the signal output from the port c is amplified by the erroramplifier 14 through the delay circuit 7, power-combiner 9, and vectoradjustor 13.

[0200] At this time, in the power-combiner 9, because no signal is inputinto the port h, the signal input into the port g is output as-is fromthe port i. The signal amplified by the error amplifier 14 is outputfrom the output terminal 2 through the power-combiner 4 and powersplitter 26.

[0201] At this time, in the power-combiner 4, because no signal is inputinto the port j, the signal input into the port k is output as-is fromthe port m.

[0202] That is, the output terminal 2 outputs the as-is output signal ofthe error amplifier 14. In this case, the control circuit 18 adjusts thevector adjustor 13 to control the level of signals input into the erroramplifier 14.

[0203] When the feedforward amplifier according to the embodiment 2 isused for a mobile communication equipment, even if the main amplifier 6fails, the direct amplification by the error amplifier 14 allows thedevice to continue operating its function though with reduced maximumoutput power, thereby achieving the improved reliability of the wholemobile communication equipment.

[0204] By the way, although the present embodiment is described for thecase where the signal level detection portion 29 is provided in adownstream stage of the power-combiner 4, the embodiment is not limitedto this. The signal level detection portion 29 may be provided betweenthe power splitter 8 and the delay circuit 10, or between the powercircuit 10 and the power-combiner 4.

[0205] (Embodiment 3)

[0206]FIG. 5 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 3 of the invention. In FIG. 5, referencenumeral 20 denotes a variable power-combiner. The control circuitswitches the switch circuit 21 and the main amplifierpower-switch-circuit 23 and also adjusts the coupling amount of thevariable power-combiner 20, depending on the signal level detected bythe signal level detection circuit 17.

[0207] By the way, the power splitter 3 of the present embodiment is anexample of the first power splitter of the invention, the vectoradjustor 5 an example of the first vector adjustor, the power splitter 8an example of the second power splitter, the delay circuit 7 an exampleof the first delay circuit, the power-combiner 9 an example of thedistortion detection power-combiner, the delay circuit 10 an example ofthe second delay circuit, the vector adjustor 13 an example of thesecond vector adjustor, the variable power-combiner 20 an example of thedistortion suppression power-combiner, the control circuit 18 an exampleof the control means, the signal level detection portion 19 an exampleof the first signal level detection means, respectively.

[0208] With the feedforward amplifier configured as described above,hereinafter, its operation will be described with reference to thedrawing.

[0209] The embodiment 3 according to invention provides the feedforwardamplifier in which, when the output power reduces considerably lowerthan the nominal output power, the error amplifier 14 directly amplifiesinput signals for outputting. When an input signal level detected by thesignal level detection circuit 17 is not lower than P2 (dBm), thecontrol circuit 18 connects the common terminal 21 a to the outputswitching terminal 21 b of the switch circuit 21 and further turns onthe main amplifier power-switch-circuit 23. At this time, thefeedforward amplifier according to the embodiment 3 of the inventionperforms the same operation as conventional feedforward amplifiers.

[0210] On the other hand, when the input signal level is not higher thanP2 (dBm), the control circuit 18 connects the common terminal 21 a tothe output switching terminal 21 c of the switch circuit 21 and turnsoff the main amplifier power-switch-circuit 23, and further changes thevariable power-combiner 20 from a loose coupling state (e.g. 10 dB) intoa tight coupling state (e.g. 3 dB). That is, when the variablepower-combiner 20 is in the tight coupling state, the degree of couplingbetween the port m and port k is 3 db, and when it is in the loosecoupling state, the degree of coupling between the port k and the port mis 10 db.

[0211] Then, an input signal input from the input terminal 1 andincluding a plurality of carrier frequency components is split into twoparts by the power splitter 3 through the power splitter 16, and the twoparts are respectively output from the port b and port c.

[0212] The signal output from the port b is absorbed by the terminatingresistor 22. Further, the signal out put from the port c is amplified bythe error amplifier 14 through the delay circuit 7, power-combiner 9,and vector adjustor 13. In this case, in the power-combiner 9, becauseno signal is input into the port h, the signal input into the port g isoutput as-is from the port i.

[0213] The signal amplified by the error amplifier 14 is output from theoutput terminal 2 through the variable power-combiner 20. At this time,in the variable power-combiner 20, because no signal is input into theport j, the signal input into the port k is output as-is from the portm. That is, the output signal of the error amplifier 14 is output as-isfrom the output terminal 2. Further, because the variable power-combiner20 is put in a tight coupling state, the signal input into the port k isoutput from the port m with less attenuation than in a loose couplingstate.

[0214] Usually, the feedforward amplifiers amplifies input signals bythe main amplifier 6, and detects and suppresses distortion componentscaused by the main amplifier 6 for outputting from the output terminal2. However, when the feedforward amplifiers amplifies input signalsdirectly by the error amplifier 14, if the level of distortions includedin the output signals of the error amplifier 14 is not higher than D1(e.g. −60 dBc) (wherein the input signal level corresponds to P2 (dBm)),it is no problem to directly output the as-is output signal of the erroramplifier 14 to the output terminal 2. At this time, because the mainamplifier power-switch-circuit 23 is turned off, the power consumed bythe main amplifier 6 becomes zero, thus improving the efficiency at lowoutput power.

[0215] Further, when the feedforward amplifier according to theembodiment 3 is used for a mobile communication equipment, even if themain amplifier 6 fails, the direct amplification by the error amplifier14 allows the device to continue operating its function though withreduced maximum output power, thereby achieving the improved reliabilityof the whole mobile communication equipment.

[0216] By the way, although the above embodiment 3 is described for thecase where the switching of the switch circuit 21 and the main amplifierpower-switch-circuit 23 and the adjusting of the variable power-combiner20 are performed depending on the input signal level, it is apparentthat the same operation can be achieved by performing the switchingdepending on the level of signals output from the port b of the powersplitter 3, the port c of the power splitter 3, or the delay circuit 7.In this case, the signal level detection portion 19 should be insertedinto the position for the signal level to be detected.

[0217] (Embodiment 4)

[0218]FIG. 6 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 4 of the invention. In FIG. 6, referencenumerals 24 and 25 denote a switch circuit. The control circuit 18switches the switch circuits 21, 24 and 25 and the main amplifierpower-switch-circuit 23 depending on the signal level detected by thesignal level detection circuit 17.

[0219] By the way, the power splitter 3 of the present embodiment is anexample of the first power splitter of the invention, the vectoradjustor 5 an example of the first vector adjustor, the power splitter 8an example of the second power splitter, the delay circuit 7 an exampleof the first delay circuit, the power-combiner 9 an example of thedistortion detection power-combiner, the delay circuit 10 an example ofthe second delay circuit, the vector adjustor 13 an example of thesecond vector adjustor, the power-combiner 4 an example of thedistortion suppression power-combiner, the control circuit 18 an exampleof the control means, the signal level detection portion 19 an exampleof the first signal level detection means, respectively.

[0220] With the feedforward amplifier configured as described above,hereinafter, its operation will be described with reference to thedrawing.

[0221] The embodiment 4 according to invention provides a feedforwardamplifier in which, when the output power reduces considerably lowerthan the nominal output power, the error amplifier 14 directly amplifiesinput signals for outputting.

[0222] When an input signal level detected by the signal level detectioncircuit 17 is not lower than P2 (dBm), the control circuit 18 connectsthe common terminal 21 a to the output switching terminal 21 b of theswitch circuit 21, a common terminal 24 a to an output switchingterminal 24 b of the switch circuit 24, and a common terminal 25 a to anoutput switching terminal 25 b of the switch circuit 25, respectively,and further turns on the main amplifier power-switch-circuit 23. At thistime, the feedforward amplifier according to the embodiment 4 of theinvention performs the same operation as conventional feedforwardamplifiers.

[0223] On the other hand, when the input signal level is not higher thanP2 (dBm), the control circuit 18 connects the common terminal 21 a tothe output switching terminal 21 c of the switch circuit 21, the commonterminal 24 a to an output switching terminal 24 c of the switch circuit24, and the common terminal 25 a to an output switching terminal 25 c ofthe switch circuit 25, respectively, and further turns off the mainamplifier power-switch-circuit 23.

[0224] At this time, an input signal input from the input terminal 1 andincluding a plurality of carrier frequency components is split into twoparts by the power splitter 3 through the power splitter 16, and the twoparts are output from the port b and port c respectively.

[0225] The signal output from the port b is absorbed by the terminatingresistor 22. Further, the signal output from the port c is amplified bythe error amplifier 14 through the delay circuit 7, power-combiner 9,and vector adjustor 13. In this case, in the power-combiner 9, becauseno signal is input into the port h, the signal input into the port g isoutput as-is from the port i. The signal amplified by the erroramplifier 14 is output from the output terminal 2 through the switchcircuits 24 and 25. That is, the output signal of the error amplifier 14is output as-is from the output terminal 2.

[0226] Usually, the feedforward amplifier amplifies input signals by themain amplifier 6, and detects and suppresses distortion componentscaused by the main amplifier 6 for outputting from the output terminal2. However, when the feedforward amplifier amplifies input signals bythe error amplifier 14 directly, if the level of distortions included inthe output signals of the error amplifier 14 is not higher than D1 (e.g.−60 dBc) (wherein the input signal level corresponds to P2 (dBm), it isno problem to output the as-is output signal of the error amplifier 14to the output terminal 2. At this time, because the main amplifierpower-switch-circuit 23 is turned off, the power consumed by the mainamplifier 6 becomes zero, allowing the improved efficiency at low outputpower. Further, when the feedforward amplifier according to theembodiment 4 is used for a mobile communication equipment, even if themain amplifier 6 fails, the direct amplification by the error amplifier14 allows the device to continue operating its function though withreduced maximum output power, thereby allowing the improved reliabilityof the whole mobile communication equipment.

[0227] By the way, although the above embodiment 4 is described for thecase where the switching of the switch circuits 21, 24 and 25 and themain amplifier power-switch-circuit 23 is performed depending on theinput signal level, it is apparent that the same operation can beachieved by performing the switching depending on the level of signalsoutput from the port b of the power splitter 3, the port c of the powersplitter 3, or the delay circuit 7. In this case, the signal leveldetection portion 19 should be inserted into the position for the signallevel to be detected.

[0228] (Embodiment 5)

[0229]FIG. 7 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 5 of the invention, of which operation willbe described with reference to the drawing hereinafter.

[0230] The embodiment 5 according to the invention has a configurationcombining the embodiments 1 and the embodiment 4.

[0231] By the way, the power splitter 3 of the present embodiment is anexample of the first power splitter of the invention, the vectoradjustor 5 an example of the first vector adjustor, the power splitter 8an example of the second power splitter, the delay circuit 7 an exampleof the first delay circuit, the power-combiner 9 an example of thedistortion detection power-combiner, the delay circuit 10 an example ofthe second delay circuit, the vector adjustor 13 an example of thesecond vector adjustor, the power-combiner 4 an example of thedistortion suppression power-combiner, the control circuit 18 an exampleof the control means, the signal level detection portion 19 an exampleof the first signal level detection means, respectively.

[0232] When the level of an input signal input from the input terminal1, detected by the signal level detection circuit 17, is not lower thanP1 (dBm), the control circuit 18 connects the common terminal 11 a tothe output switching terminal 11 b of the switch circuit 11, the commonterminal 21 a to the output switching terminal 21 b of the switchcircuit 21, the common terminal 24 a to the output switching terminal 24b of the switch circuit 24, and the common terminal 25 a to the outputswitching terminal 25 b of the switch circuit 25, respectively, andfurther turns on the main amplifier power-switch-circuit 23 and theerror amplifier power switch circuit 15. In this case, the feedforwardamplifier according to the embodiment 5 of the invention performs thesame operation as conventional feedforward amplifiers.

[0233] On the other hand, when the input signal level is not lower thanP2 (dBm) and not higher than P1 (dBm), the control circuit 18 connectsthe common terminal 11 a to the output switching terminal 11 c of theswitch circuit 11, the common terminal 21 a to the output switchingterminal 21 b of the switch circuit 21, and the common terminal 25 a tothe output switching terminal 25 b of the switch circuit 25,respectively, and further turns on the main amplifierpower-switch-circuit 23 and turns off the error amplifier power switchcircuit 15. For the switch circuit 24, the common terminal 24 a may beconnected to any one of the output switching terminals 24 b and 24 c. Inthis case, because the level of distortions included in the outputsignal of the main amplifier 6 is D1 (e.g. −60 dBc), the output signalof the main amplifier 6 is output as-is from the output terminal 2.

[0234] Further, when the input signal level is not higher than P2 (dBm),the control circuit 18 connects the common terminal 11 a to the outputswitching terminal 11 b of the switch circuit 11, the common terminal 21a to the output switching terminal 21 c of the switch circuit 21, thecommon terminal 24 a to the output switching terminal 24 c of the switchcircuit 24, and the common terminal 25 a to the output switchingterminal 25 c of the switch circuit 25, respectively, and further turnson the error amplifier power switch circuit 15 and turns off the mainamplifier power-switch-circuit 23. In this case, because the inputsignal is directly amplified by the error amplifier 14 and the level ofdistortions included in the output signal of the error amplifier 14 isnot higher than D1 (e.g. −60 dBc), the output signal of the erroramplifier 14 is output as-is from the output terminal 2.

[0235] Such a configuration of FIG. 7 can improve the efficiency at lowoutput power. Further, when the feedforward amplifier according to theembodiment 5 is used for a mobile communication equipment, even if themain amplifier 6 fails, the direct amplification by the error amplifier14 allows the device to continue operating its function though withreduced maximum output power, thereby allowing the improved reliabilityof the whole mobile communication equipment.

[0236] By the way, although the above embodiment 5 is described for thecase where the switching of the switch circuits 11, 21, 24, and 25, themain amplifier power-switch-circuit 23 and the error amplifier powerswitch circuit 15 is performed depending on the input signal level, itis apparent that the same operation can be achieved by performing theswitching depending on the level of signals output from the port b ofthe power splitter 3, the port c of the power splitter 3, or the delaycircuit 7. In this case the signal level detection portion 19 should beinserted into the position for the signal level to be detected.

[0237] (Embodiment 6)

[0238]FIG. 8 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 6 of the invention. In FIG. 8, referencenumerals 31 and 36 denote power splitters, 32 and 37 power-combiners, 33a switch circuit, 34 a terminating resistor, 35 and 38 delay circuits,39 a vector adjustor, 40 a power amplifier, 41 a power amplifier powerswitch circuit, respectively. The power splitters 3, 8, and 31, thepower-combiners 4 and 9, the vector adjustors 5 and 13, the mainamplifier 6, the delay circuits 7 and 10, the error amplifier 14, theswitch circuits 21 and 24, the main amplifier power-switch-circuit 23and the terminating resistor 22 constitute a first feedforward amplifiercircuit 42. Further, the power splitters 31 and 36, the power-combiners32 and 37, the vector adjustors 13 and 39, the error amplifier 14, thedelay circuits 35 and 38, the power amplifier 40, the switch circuits 24and 33, the power amplifier power switch circuit 41, and the terminatingresistor 34 constitute a second feedforward amplifier circuit 43.Further, the symbols o to z added to the power splitters 31 and 36 andthe power-combiners 32 and 37 denotes each port.

[0239] By the way, the power splitter 3 of the present embodiment is anexample of the first splitter of the invention, the vector adjustor 5 anexample of the first vector adjustor, the power splitter 8 an example ofthe second power splitter, the delay circuit 7 an example of the firstdelay circuit, the power-combiner 9 an example of the distortiondetection power-combiner, the delay circuit 10 an example of the seconddelay circuit, the vector adjustor 13 an example of the second vectoradjustor, the power-combiner 4 an example of the distortion suppressionpower-combiner, the control circuit 18 an example of the control means,the signal level detection portion 19 an example of the first signallevel detection means, the power splitter 36 an example of the thirdpower splitter, the delay circuit 38 an example of the third delaycircuit, the power splitter 3 an example of the fourth power splitter,the delay circuit 35 an example of the fourth delay circuit, thepower-combiner 37 an example of the second distortion detectionpower-combiner, the vector adjustor 39 an example of the third vectoradjustor, the power amplifier 40 an example of the second erroramplifier, and the power-combiner 32 an example of the second distortionsuppression power-combiner, respectively.

[0240] With the feedforward amplifier configured as described above, itsoperation will be described with reference to the drawing hereinafter.

[0241] An input signal input from an input terminal 1 and including aplurality of carrier frequency components is input into the port a ofthe power splitter 3 through the power splitter 16. At this time, partof the input signal is took out from the port n of the power splitter 16and input into the signal level detection circuit 17. The signal inputinto the port a of the power splitter 3 is split into two parts, whichare output from the port b and port c respectively.

[0242] The signal output from the port b is input into the commonterminal 21 a of the switch circuit 21.

[0243] Here, when the input signal level detected by the signal leveldetection circuit 17 is not lower than P3 (dBm), the control circuit 18connects the common terminal 21 a to the output switching terminal 21 bof the switch circuit 21, the common terminal 24 a to the outputswitching terminal 24 b of the switch circuit 24, the common terminal 25a to the output switching terminal 25 b of the switch circuit 25, andthe common terminal 33 a to the output switching terminal 33 c of theswitch circuit 33, respectively, and further turns on the main amplifierpower-switch-circuit 23 and turns off the power amplifier power switchcircuit 41.

[0244] On the other hand, when the input signal level is not higher thanP3 (dBm), the control circuit 18 connects the common terminal 21 a tothe output switching terminal 21 c of the switch circuit 21, the commonterminal 24 a to the output switching terminal 24 c of the switchcircuit 24, the common terminal 25 a to the output switching terminal 25c of the switch circuit 25, and the common terminal 33 a to the outputswitching terminal 33 b of the switch circuit 33, respectively, andturns on the power amplifier power switch circuit 41 and further turnsoff the main amplifier power-switch-circuit 23.

[0245] First, when the input signal level is not lower than P3 (dBm),the signal input into the common terminal 21 a of the switch circuit 21is amplified by the main amplifier 6 through the output switchingterminal 21 b and the vector adjustor 5, and input into the port j ofthe power-combiner 4 through the power splitter 8 and the delay circuit10. At this time, signals including distortion components caused byintermodulation due to the non-linearity of the main amplifier 6 inaddition to the carrier frequency components are input into the port j.Further, part of the output signal of the main amplifier 6 is took outfrom the port f of the power splitter 8, and input into the port h ofthe power-combiner 9.

[0246] On the other hand, the signal output from the port c is inputinto the port g of the power-combiner 9 through the delay circuit 7.Here, the vector adjustor 5 and the delay circuit 7 are adjusted suchthat the carrier frequency components of the signals input into the portg and the port h may have the same amplitudes and opposite phases, bywhich a signal having only the distortion components with the carrierfrequency components canceled out is output from the port i.

[0247] Next, the signal output from the port i is split into two partsby the power splitter 31 and the two parts are output from a port p andport q respectively. The signal out put from the port q is absorbed bythe terminating resistor 34 through the switch circuit 33. The signaloutput from the port p is amplified by the error amplifier 14 throughthe vector adjustor 13, and input into the port k of the power splitter4 through the switch circuit 24. Here, the vector adjustor 13 and thedelay circuit 10 are adjusted such that the distortion components of thesignals input into the port j and the port k may have the sameamplitudes and opposite phases, thereby a signal having only the carrierfrequency components with the distortion components canceled out beingoutput from the port m of the power-combiner 4. The signal output fromthe port m is output from the output terminal 2 through the switchcircuit 25.

[0248] On the other hand, when the input signal level is not higher thanP3 (dBm), the signal input into the common terminal 21 a of the switchcircuit 21 is absorbed by the terminating resistor 22 through the outputswitching terminal 21 c. Further, the signal output from the port c isinput into a port o of the power splitter 31 through the delay circuit 7and the power-combiner 9. At this time, in the power-combiner 9, becauseno signal is input into the port h, the signal input into the port g isoutput as-is from the port i. The signal input into the port o of thepower splitter 31 is split into two parts, which are output from theport p and port q respectively. The signal output from the port p isamplified by the error amplifier 14 through the vector adjustor 13, andinput into a port x of the power-combiner 32 through the switch circuit24, power splitter 36 and delay circuit 38.

[0249] At this time, signals including distortion components caused byintermodulation due to the non-linearity of the error amplifier 14 inaddition to the carrier frequency components are input into the port x.Further, part of the output signal of the switch circuit 24 is took outfrom a port t of the power splitter 36, and input into a port v of thepower-combiner 37. On the other hand, the signal output from the port qis input into a port u of the power-combiner 37 through the switchcircuit 33 and the delay circuit 35.

[0250] Here, the vector adjustor 13 and the delay circuit 35 areadjusted such that the carrier frequency components of the signals inputinto the port u and the port v may have the same amplitudes and oppositephases. Thereby, a signal having only the distortion components with thecarrier frequency components canceled out is output from a port w.

[0251] Then, the signal output from the port w is amplified by the poweramplifier 40 through the vector adjustor 39 and input into a port y ofthe power-combiner 32. Here, the vector adjustor 39 and the delaycircuit 38 are adjusted such that the distortion components of thesignals input into the port x and the port y may have the sameamplitudes and opposite phases. Thereby, a signal having only thecarrier frequency components with the distortion components canceled outis output from a port z of the power-combiner 32. The signal output fromthe port z is output from the output terminal 2 through the switchcircuit 25.

[0252] That is, when the input signal level is not lower than P3 (dBm),the first feedforward amplifier circuit 42 amplifies the input signal,and when the input signal level is not higher than P3 (dBm), the secondfeedforward amplifier circuit 43 amplifies the input signal. The powerconsumed by the power amplifier 40 is much less than that by the mainamplifier 6. Further, because the error amplifier 14 is made for lowerpower when compared to the main amplifier 6, the power consumed by theerror amplifier 14 is less than that by the main amplifier.

[0253] Such a configuration of FIG. 8 can improve the efficiency, since,at low output power, the power consumed by the main amplifier becomeszero while the power consumed by the power amplifier 40 increases.Further, when the feedforward amplifier according to the embodiment 6 isused for a mobile communication equipment, even if the main amplifier 6fails, the device can continue operating its function though withreduced maximum output power, thereby allowing the improved reliabilityof the whole mobile communication equipment.

[0254] By the way, although the above embodiment 6 is described for thecase where the switching of the switch circuits 21, 24, 25 and 33, themain amplifier power-switch-circuit 23 and the power amplifier powerswitch circuit 41 are performed depending on the input signal level, itis apparent that the same operation can be achieved by performing theswitching depending on the level of signals output from the port b ofthe power splitter 3, the port c of the power splitter 3, or the delaycircuit 7. In this case, the signal level detection portion 19 should beinserted into the position for the signal level to be detected.

[0255] (Embodiment 7)

[0256]FIG. 9 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 7 of the invention, of which operation willbe described with reference to the drawing hereinafter.

[0257] The embodiment 7 according to the invention has a configurationcombining the embodiments 1 and the embodiment 6.

[0258] By the way, the power splitter 3 of the present embodiment is anexample of the first power splitter of the invention, the vectoradjustor 5 an example of the first vector adjustor, the power splitter 8an example of the second power splitter, the delay circuit 7 an exampleof the first delay circuit, the power-combiner 9 an example of thedistortion detection power-combiner, the delay circuit 10 an example ofthe second delay circuit, the vector adjustor 3 an example of the secondvector adjustor, the power-combiner 4 an example of the distortionsuppression power-combiner, the control circuit 18 an example of thecontrol means, the signal level detection portion 19 an example of thefirst signal level detection means, the power splitter 36 an example ofthe third power splitter, the delay circuit 38 an example of the thirddelay circuit, the power splitter 31 an example of the fourth powersplitter, the delay circuit 35 an example of the fourth delay circuit,the power-combiner 37 an example of the second distortion detectionpower-combiner, the vector adjustor 39 an example of the third vectoradjustor, the power amplifier 40 an example of the second erroramplifier, and the power-combiner 32 an example of the second distortionsuppression power-combiner, respectively.

[0259] When the level of an input signal input from the input terminal1, detected by the signal level detection circuit 17, is not lower thanP3 (dBm) the control circuit 18 connects the common terminal 11 a to theoutput switching terminal 11 b of the switch circuit 11, the commonterminal 21 a to the output switching terminal 21 b of the switchcircuit 21, the common terminal 24 a to the output switching terminal 24b of the switch circuit 24, the common terminal 25 a to the outputswitching terminal 25 b of the switch circuit 25, and the commonterminal 33 a to the output switching terminal 33 c of the switchcircuit 33, respectively, and further turns on the main amplifierpower-switch-circuit 23 and the error amplifier power switch circuit 15and turns off the power amplifier power switch circuit 41. In this case,the input signal is amplified by the first feedforward amplifier circuit42 and output from the output terminal 2.

[0260] On the other hand, when the input signal level is not lower thanP1 (dBm) and not higher than P3 (dBm), the control circuit 18 connectsthe common terminal 11 a to the output switching terminal 11 b of theswitch circuit 11, the common terminal 21 a to the output switchingterminal 21 c of the switch circuit 21, the common terminal 24 a to theoutput switching terminal 24 c of the switch circuit 24, the commonterminal 25 a to the output switching terminal 25 c of the switchcircuit 25, and the common terminal 33 a to the output switchingterminal 33 b of the switch circuit 33, respectively, and further turnson the error amplifier power switch circuit 15 and the power amplifierpower switch circuit 41 and turns off the main amplifierpower-switch-circuit 23. In this case, the input signal is amplified bythe second feedforward amplifier circuit 43 and output from the outputterminal 2.

[0261] Further, when the input signal level is not higher than P1 (dBm)the control circuit 18 connects the common terminal 11 a to the outputswitching terminal 11 c of the switch circuit 11, the common terminal 21a to the output switching terminal 21 b of the switch circuit 21, thecommon terminal 25 a to the output switching terminal 25 b of the switchcircuit 25, and the common terminal 33 a to the output switchingterminal 33 c of the switch circuit 33, respectively, and further turnson the main amplifier power-switch-circuit 23 and turns off the erroramplifier power switch circuit 15 and the power amplifier power switchcircuit 41. For the switch circuit 24, the common terminal 24 a may beconnected to any one of the output switching terminals 24 b and 24 c. Inthis case, because the level of distortions included in the outputsignal of the main amplifier 6 is not higher than D1 (e.g. −60 dBc), theoutput signal of the main amplifier 6 is output as-is from the outputterminal 2.

[0262] Such a configuration of FIG. 9 can improve the efficiency at lowoutput power. Further, when the feedforward amplifier according to theembodiment 7 is used for a mobile communication equipment, even if themain amplifier 6 fails, the device can continue operating its functionthough with reduced maximum output power, thereby allowing the improvedreliability of the whole mobile communication equipment.

[0263] By the way, although the above embodiment 7 is described for thecase where the switching of the switch circuits 11, 21, 24, 25 and 33,the main amplifier power-switch-circuit 23, error amplifier power switchcircuit 15, and the power amplifier power switch circuit 41 areperformed depending on the input signal level, it is apparent that thesame operation can be achieved by performing the switching depending onthe level of signals output from the port b of the power splitter 3, theport c of the power splitter 3, or the delay circuit 7. In this case,the signal level detection portion 19 should be inserted into theposition for the signal level to be detected.

[0264] (Embodiment 8)

[0265]FIG. 10 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 8 of the invention.

[0266] The same portions of the feedforward amplifier of the embodiment8 as the feedforward amplifier of the embodiment 5 will be denoted bythe same symbols as the embodiment 5 and the detailed descriptionthereof will be omitted.

[0267]FIG. 10 of the embodiment 8 is different from FIG. 7 of theembodiment 5 in the following points.

[0268] That is, in the feedforward amplifier of FIG. 10, the port k ofthe power-combiner 4 is connected to the output of the error amplifier14, and the port j of the power amplifier is connected to the output ofthe delay circuit 10. Further, a port p of an antenna-shared circuit 51is connected to the port m of the power-combiner 4. Further, a port r ofthe antenna-shared circuit 51 is connected to an antenna 50 and a port qof the antenna-shared circuit 51 is connected to the input of thereceiving circuit 52. The output of the receiving circuit 52 isconnected to a received-signal output terminal 55. Further, a signallevel detection circuit 53 is connected to the receiving circuit 52, anda control circuit 54 is connected to the output of the signal leveldetection circuit 53. The others are the same as the embodiment 5.

[0269] By the way, the power splitter 3 of the present embodiment is anexample of the first power splitter of the invention, the vectoradjustor 5 an example of the first vector adjustor, the power splitter 8an example of the second power splitter, the delay circuit 7 an exampleof the first delay circuit, the power-combiner 9 an example of thedistortion detection power-combiner, the delay circuit 10 an example ofthe second delay circuit, the vector adjustor 13 an example of thesecond vector adjustor, the power-combiner 4 an example of thedistortion suppression power-combiner, the control circuit 18 an exampleof the control means, the signal level detection circuit 53 an exampleof the first signal level detection means, respectively.

[0270] Next, the present embodiment as such will be described centeringon the points different from the embodiment 5.

[0271] In the embodiment 5, the signal detection circuit 17 detects theinput signal level of an input signal input from the input terminal 1,and the control circuit 18 controls the switch circuit 11 and the likebased on the detected input signal level. On the other hand, in thepresent embodiment, the signal level detection circuit 53 detects thelevel of a received signal of an incoming wave received by the antenna50. Also, the control circuit 54 controls the switch circuit 11 and thelike based on the level of the received signal detected.

[0272] That is, the antenna-shared circuit 51 introduces the incomingwave received by the antenna 50 as a received signal into the receivingcircuit 52, And also introduces a transmitting signal output from theport m of the power-combiner 4 to the antenna 50.

[0273] The receiving circuit 52 processes the received signal outputfrom the port q of the antenna-shared circuit 51 for outputting to thereceived-signal output terminal 55, and also outputs the processedreceived-signal to the signal level detection circuit 53.

[0274] The signal level detection circuit 53 detects the received-signallevel of the received signal output from the receiving circuit 52.

[0275] Generally, when the level of the received-signal received by theantenna 50 is low, the partner device is considered to exist at adistant place or at a place from which radio wave is difficult to reachthe antenna. Therefore, it is necessary to transmit a transmitting waveof high power from the antenna 50 such that the partner device mayreceive satisfactorily the transmitting wave. Alternatively, when thereceived-signal level of the received-signal received by the antenna 50is high, the partner device is considered to exist at a near place or ata place from which radio wave is easy to reach the antenna. Therefore,transmission of a transmitting wave of low power to the partner devicestill allows the partner device to receive satisfactorily thetransmitting wave.

[0276] Therefore, when the level of received signals output from thereceiving circuit 52 and detected by the signal level detection circuit53 is not higher than P2 (dBm), the control circuit 54 connects thecommon terminal 11 a to the output switching terminal 11 b of the switchcircuit 11 and the common terminal 21 a to the output switching terminal21 b of the switch circuit 21, respectively, and further turns on themain amplifier power-switch-circuit 23 and the error amplifier powerswitch circuit 15. In this case, the feedforward amplifier according tothe present embodiment operates in the same manner as conventionalfeedforward amplifiers.

[0277] On the other hand, when the level of received-signals output fromthe receiving circuit 52 and detected by the signal level detectioncircuit 53 is not lower than P2 (dBm) and not higher than P1 (dBm), thecontrol circuit 54 connects the common terminal 11 a to the outputswitching terminal 11 c of the switch circuit 11 and the common terminal21 a to the output switching terminal 21 c of the switch circuit 21,respectively, and further turns on the main amplifierpower-switch-circuit 23 and turns off the error amplifier power switchcircuit 15. In this case, because the level of distortions included inthe output signal of the main amplifier 6 is not higher than D1 (e.g.−60 dBc), the output signal of the main amplifier 6 is output as-is fromthe port m of the power-combiner 4.

[0278] Further, when the input signal level is not lower than P1 (dBm),the control circuit 54 connects the common terminal 11 a to the outputswitching terminal 11 b of the switch circuit 11 and the common terminal21 a to the output switching terminal 21 c of the switch circuit 21,respectively, and further turns on the error amplifier power switchcircuit 15 and turns off the main amplifier power-switch-circuit 23. Inthis case, because the input signal is amplified directly by the erroramplifier 14 and the level of distortions included in the output signalof the error amplifier 14 is not higher than D1 (e.g. −60 dBc), theoutput signal of the error amplifier 14 is output as-is from the port mof the power-combiner 4.

[0279] Therefore, the configuration of FIG. 10 can improve theefficiency at low output power. Further, when the feedforward amplifieraccording to the embodiment 8 is used for a mobile communicationequipment, even if the main amplifier 6 fails, the direct amplificationby the error amplifier 14 allows the device to continue operating itsfunction though with reduced maximum output power, thereby allowing theimproved reliability of the whole mobile communication equipment.

[0280] By the way, although the above embodiment 8 performs theswitching of the switch circuits 11 and 21, the main amplifierpower-switch-circuit 23, and the error amplifier power switch circuit 15depending on the level of the received signal processed by the receivingcircuit 52, it is apparent that the same operation can be achieved byperforming the switching depending on the level of the received signalbefore being processed by the receiving circuit 52 or the level of thereceived signal in the course of being processed by the receivingcircuit 52.

[0281] By the way, with each of the feedforward amplifiers describedreferring to FIGS. 1, 4, 5, 6, 7, 8, and 9, instead of detecting thesignal level of input signals by the signal level detection circuit 17,the signal level detection circuit 52 may be used to detect the signallevel of received signals from the receiving circuit 52 in the samemanner as the embodiment 8, and then the control circuit may controleach switch circuit and the like based on the detected signal level.

[0282] However, when the signal level of received signals from thereceiving circuit 52 is detected and the control circuit controls eachswitch circuit and the like based on the detected signal level, theamplitude of the detected signal level is inverse to that in the casewhere the controlling is performed in the feedforward amplifiersdescribed in each of the embodiments.

[0283] For example, in the feedforward amplifier of FIG. 1 described inassociation with the embodiment 1, when the detected signal level of thereceived signal from the receiving circuit 52 is not higher than P1(dBm), the control circuit 18 should connect the common terminal 11 a tothe output switching terminal 11 b of the switch circuit 11, and alsoturn on the error amplifier power switch circuit 15. On the other hand,when the input signal level is higher than P1 (dBm), the control circuit18 should connect the common terminal 11 a to the output switchingterminal 11 c of the switch circuit 11, and also turn off the erroramplifier power switch circuit 15.

[0284] When the signal level of received signals from the receivingcircuit 52 is detected and the control circuit controls each switchcircuit and the like based on the detected signal level in the abovemanner, the controlling should be performed such that the amplitude ofthe detected signal level may be inverse to that in the case where thecontrolling is performed by the feedforward amplifiers described in eachof the embodiments. The others are the same as each of the embodiments.

[0285] (Embodiment 9)

[0286]FIG. 11 shows a configuration diagram of the feedforward amplifieraccording to the embodiment 9 of the invention.

[0287] The same portions of the feedforward amplifier of the embodiment9 as the feedforward amplifier of the embodiment 5 will be denoted bythe same symbols as the embodiment 5 and the detailed descriptionthereof will be omitted.

[0288]FIG. 11 of the embodiment 9 is different from FIG. 7 of theembodiment 5 in the following points.

[0289] That is, a baseband signal generating portion 56 performs bothfunctions of the signal level detection circuit and the control circuitof the embodiment 7. Further, the baseband signal generating portion 56is connected to a transmitting circuit 57, which is connected to theport a of the power splitter 3.

[0290] By the way, the power splitter 3 of the present embodiment is anexample of the first power splitter of the invention, the vectoradjustor 5 an example of the first vector adjustor, the power splitter 8an example of the second power splitter, the delay circuit 7 an exampleof the first delay circuit, the power-combiner 9 an example of thedistortion detection power-combiner, the delay circuit 10 an example ofthe second delay circuit, the vector adjustor 13 an example of thesecond vector adjustor, the power-combiner 4 an example of thedistortion suppression power-combiner, the baseband signal generatingportion 56 an example of the control means, respectively, and thebaseband signal generating portion 56 also serves as an example of thefirst signal level detection means.

[0291] Next, the present embodiment as such will be described centeringon the points different from the embodiment 5.

[0292] The baseband signal generating portion 56 generates a basebandsignal from signals input from a microphone and the like not shown, andoutputs the baseband signal to a transmitting circuit 57. Thetransmitting circuit 57 modulates the baseband signal incoming from thebaseband signal generating portion 56, converting the baseband signalinto a modulated signal and a transmitting frequency which are output tothe port a of the power splitter.

[0293] Further, the baseband signal generating portion 56 detects thesignal level of the baseband signal.

[0294] Then, when the signal level of baseband signals detected by thebaseband signal generating portion 56 is not lower than P1 (dBm), thebaseband signal generating portion 56 connects the common terminal 11 ato the output switching terminal 11 b of the switch circuit 11 and thecommon terminal 21 a to the output switching terminal 21 b of the switchcircuit 21, respectively, and further turns on the main amplifierpower-switch-circuit 23 and the error amplifier power switch circuit 15.In this case, the feedforward amplifier according to the embodiment 9operates in the same manner as conventional feedforward amplifiers.

[0295] On the other hand, when the signal level of baseband signalsdetected by the baseband signal generating portion 56 is not lower thanP2 (dBm) and not higher than P1 (dBm), the baseband signal generatingportion 56 connects the common terminal 11 a to the output switchingterminal 11 c of the switch circuit 11 and the common terminal 21 a tothe output switching terminal 21 b of the switch circuit 21,respectively, and further turns on the main amplifierpower-switch-circuit 23 and turns off the error amplifier power switchcircuit 15. In this case, because the level of distortions included inthe output signal of the main amplifier 6 is not higher than D1 (e.g.−60 dBc), the output signal of the main amplifier 6 is output as-is fromthe output terminal 2.

[0296] Further, when the signal level of baseband signals detected bythe baseband signal generating portion 56 is not higher than P2 (dBm),the baseband signal generating portion 56 connects the common terminal11 a to the output switching terminal 11 b of the switch circuit 11 andthe common terminal 21 a to the output switching terminal 21 c of theswitch circuit 21, respectively, and further turns on the erroramplifier power switch circuit 15 and turns off the main amplifierpower-switch-circuit 23. In this case, because the input signal isdirectly amplified by the error amplifier 14 and the level ofdistortions included in the output signal of the error amplifier 14 isnot higher than D1 (e.g. −60 dBc), the output signal of the erroramplifier 14 is output as-is from the output terminal 2.

[0297] Generally, when the level of baseband signals is high, the outputsignal of the output terminal 2 becomes of high power, and when thelevel of baseband signals is low, the output signal of the outputterminal 2 becomes of low power.

[0298] Therefore, the configuration of FIG. 11 can improve theefficiency at low output power. Further, when the feedforward amplifieraccording to the embodiment 9 is used for a mobile communicationequipment, even if the main amplifier 6 fails, the direct amplificationby the error amplifier 14 allows the device to continue operating itsfunction though with reduced maximum output power, thereby allowing theimproved reliability of the whole mobile communication equipment.

[0299] By the way, although the above embodiment 9 performs theswitching of the switch circuits 11 and 21, the main amplifierpower-switch-circuit 23 and the error amplifier power switch circuit 15depending on the signal level of baseband signals from the basebandsignal generating portion 56, it is apparent that the same operation canbe obtained by performing the switching depending on the signal level ofinput signals input from a microphone and the like into the basebandsignal generating portion 56 or the signal level of baseband signals inthe course of being processed by the baseband signal generating portion56 or the signal level of baseband signals output from the basebandsignal generating portion 56. Further, it is apparent that the sameoperation can be obtained by performing the switching depending on thesignal level of signals in the course of being processed by thetransmitting circuit 57 or the signal level of transmitting signalsoutput from the transmitting circuit 57.

[0300] By the way, with each of the feedforward amplifiers describedreferring to FIGS. 1, 4, 5, 6, 7, 8, and 9, instead of detecting thesignal level of input signals input from the input terminal 1 by thesignal level detection circuit 17, the signal level of baseband signalsmay be detected in the same manner as the embodiment 9 and each switchcircuit and the like may be controlled based on the detected signallevel.

[0301] It has been described that the feedforward amplifier according tothe embodiment 3 uses the variable power-combiner 20, and when itoperates both the main amplifier 6 and error amplifier 13, the variablepower-combiner 20 is in a loose coupling state and the main amplifier 6is also stopped, and, when it operates the error amplifier 13 only, thevariable power-combiner 20 is in a tight coupling state. However, thevariable power-combiner 20 may be used for the feedforward amplifiersother than that of the embodiment 3 to perform the same operation. Thiscan improve further the efficiency of the feedforward amplifieraccording to the present embodiment.

[0302] Further, with the feedforward amplifier according to theembodiment 4, it has been described that, at low output power, theswitch circuits 24 and 25 are used to output signals without passingthrough the power-combiner 4. However, the same operation may be appliedto the feedforward amplifiers other than that of the embodiment 4. Thiscan improve further the efficiency of the feedforward amplifieraccording to the present embodiment.

[0303] Further, when an abnormal event occurs in the main amplifier, theerror amplifier can be used to amplify and output the input signal,thereby allowing the improved reliability of mobile communicationequipments using the feedforward amplifier.

[0304] Furthermore, communication equipments comprising a basebandsignal generating portion for generating a baseband signal and atransmitting circuit for generating a transmitting signal from thebaseband signal generated, in which the feedforward amplifiers accordingto the invention is used for the above described transmitting circuit isincluded in the invention.

[0305] Further, the communication equipments according to the inventionrefer to base station devices of mobile communication equipment such asportable telephones, PHS and car telephones.

[0306] As apparent from the above description, the invention can providea feedforward amplifier and a mobile communication equipment of whichefficiency does not reduce even at reduced output power.

[0307] Further, the invention can provide a feedforward amplifier and amobile communication equipment of which communication does not stopcompletely even if the main amplifier fails.

What is claimed is:
 1. A feedforward amplifier comprising: a first powersplitter for splitting an input signal into two parts; a first vectoradjustor for adjusting the amplitude and phase of one output signal ofsaid first power splitter; a main amplifier for amplifying an outputsignal of said first vector adjustor; a second power splitter forsplitting an output signal of said main amplifier into two parts; afirst delay circuit for delaying the other output signal of said firstpower splitter; a distortion detection power-combiner for synthesizingone output signal of said second power splitter and an output signal ofsaid first delay circuit; a second delay circuit for delaying the otheroutput signal of said second power splitter; a second vector adjustorfor adjusting the amplitude and phase of the output signal of saiddistortion detection power-combiner; an error amplifier for amplifyingthe output signal of said second vector adjustor; a distortionsuppression power-combiner for synthesizing the output signal of saidsecond delay circuit and the output signal of said error amplifier; andcontrol means of at least stopping the operation of said error amplifieror said main amplifier depending on a predetermined condition.
 2. Thefeedforward amplifier according to claim 1, further comprising: firstsignal level detection means of detecting a first signal level that isthe signal level of said input signal, or the signal level of a basebandsignal in a baseband signal generating portion, or the signal level of atransmitting signal in a transmitting circuit, wherein saidpredetermined condition represents said first signal level, and whensaid detected first signal level is not higher than a predeterminedvalue, said control means stops the operation of said error amplifier.3. The feedforward amplifier according to claim 1, further comprising:first signal level detection means of detecting a first signal levelthat is the signal level of a received signal in a receiving circuit,wherein said predetermined condition represents said first signal level,and when said detected first signal level is not lower than apredetermined value, said control means stops the operation of saiderror amplifier.
 4. The feedforward amplifier according to claim 1,further comprising: first signal level detection means of detecting afirst signal level that is the signal level of said input signal, or thesignal level of a baseband signal in a baseband signal generatingportion, or the signal level of a transmitting signal in a transmittingcircuit, or the signal level of a received signal in a receivingcircuit; and second signal level detection means of detecting a secondsignal level that is the signal level of said output signal, whereinsaid predetermined condition represents gain of said second signal levelto said first signal level, and when said gain is out of a predeterminedvalue, said control means stops the operation of said main amplifier. 5.The feedforward amplifier according to claim 1, further comprising:first signal level detection means of detecting a first signal levelthat is the signal level of an input signal, or the signal level of abaseband signal in a baseband signal generating portion, or the signallevel of a transmitting signal in a transmitting circuit, wherein saidpredetermined condition represents said first signal level, and whensaid first signal level is not higher than a predetermined value, saidcontrol means stops the operation of said main amplifier.
 6. Thefeedforward amplifier according to claim 1, further comprising: firstsignal level detection means of detecting a first signal level that isthe signal level of a received signal in a receiving circuit, whereinsaid predetermined condition represents said first signal level, andwhen said first signal level is not lower than a predetermined value,said control means stops the operation of said main amplifier.
 7. Thefeedforward amplifier according to claim 4 or 5, wherein said distortionsuppression power-combiner is a variable power-combiner that can have atight coupling state and a loose coupling state, and when said firstsignal level is higher than a predetermined value, said control meanscontrols said variable power-combiner to have said loose coupling state,and when said first signal level is not higher than the predeterminedvalue, said control means controls said variable power-combiner to havesaid tight coupling state.
 8. The feedforward amplifier according toclaim 4 or 6, wherein said distortion suppression power-combiner is avariable power-combiner that can have a tight coupling state and a loosecoupling state, when said first signal level is lower than apredetermined value, said control means controls said variablepower-combiner to have said loose coupling state, and when said firstsignal level is not lower than the predetermined value, said controlmeans controls said variable power-combiner to have said tight couplingstate.
 9. The feedforward amplifier according to claim 4 or 5, wherein,when said first signal level is not higher than a predetermined value,said control means performs such control that the output signal of saiderror amplifier can be output without passing through said distortionsuppression power-combiner.
 10. The feedforward amplifier according toclaim 4 or 6, wherein, when said first signal level is not lower than apredetermined value, said control means performs such control that theoutput signal of said error amplifier can be output without passingthrough said distortion suppression power-combiner.
 11. The feedforwardamplifier according to claim 1, further comprising: first signal leveldetection means of detecting a first signal level that is the signallevel of an input signal, or the signal level of a baseband signal in abaseband signal generating portion, or the signal level of atransmitting signal in a transmitting circuit, wherein saidpredetermined condition represents said first signal level, and whensaid first signal level is not higher than a first predetermined valueand higher than a second predetermined value that is smaller than saidfirst predetermined value, said control means stops the operation ofsaid error amplifier, and when said first signal level is not higherthan said second predetermined value, said control means stops theoperation of said main amplifier.
 12. The feedforward amplifieraccording to claim 1, further comprising: first signal level detectionmeans of detecting a first signal level that is the signal level of areceived signal in a receiving circuit, wherein said predeterminedcondition represents said first signal level, and when said first signallevel is not higher than a first predetermined value and higher than asecond predetermined value that is smaller than said first predeterminedvalue, said control means stops the operation of said error amplifier,and when said first signal level is not lower than said firstpredetermined value, said control means stops the operation of said mainamplifier.
 13. The feedforward amplifier according to claim 1, furthercomprising: a third power splitter for splitting the output signal ofsaid error amplifier into two parts; a third delay circuit for delayingone output signal of said third power splitter; a fourth power splitterfor splitting the output signal of said distortion suppressionpower-combiner into two parts; a fourth delay circuit for delaying oneoutput signal of said fourth power splitter; a second distortiondetection power-combiner for synthesizing the output signal of saidfourth delay circuit and the other output signal of said third powersplitter; a third vector adjustor for adjusting the amplitude and phaseof the output signal of said second distortion detection power-combiner;a second error amplifier for amplifying the output signal of said thirdvector adjustor; a second distortion suppression power-combiner forsynthesizing the output signal of said third delay circuit and theoutput signal of said second error amplifier; and first signal leveldetection means of detecting a first signal level that is the signallevel of said input signal, or the signal level of a baseband signal ina baseband signal generating portion, or the signal of a transmittingsignal in a transmitting circuit, wherein said control means also stopsthe operation of said second error amplifier depending on saidpredetermined condition, said predetermined condition represents saidfirst signal level, and when said first signal level is higher than apredetermined value, said control means stops the operation of saidsecond error amplifier and performs such control that the output signalof said error amplifier can not be input by said third power splitter,and performs such control that the output signal of said distortionsuppression power-combiner can be output to the outside, and when saidfirst signal level is not higher than the predetermined value, saidcontrol means stops the operation of said main amplifier and performssuch control that the output signal of said error amplifier can not beinput by said distortion suppression power-combiner but can be input bysaid third power splitter, and performs such control that the outputsignal of said second distortion suppression power-combiner can beoutput to the outside.
 14. The feedforward amplifier according to claim1, further comprising: a third power splitter for splitting the outputsignal of said error amplifier into two parts; a third delay circuit fordelaying one output signal of said third power splitter; a fourth powersplitter for splitting the output signal of said distortion suppressionpower-combiner into two parts; a fourth delay circuit for delaying oneoutput signal of said fourth power splitter; a second distortiondetection power-combiner for synthesizing the output signal of saidfourth delay circuit and the other output signal of said third powersplitter; a third vector adjustor for adjusting the amplitude and phaseof the output signal of said second distortion detection power-combiner;a second error amplifier for amplifying the output signal of said thirdvector adjustor; a second distortion suppression power-combiner forsynthesizing the output signal of said third delay circuit and theoutput signal of said second error amplifier; and first signal leveldetection means of detecting a first signal level that is the signallevel of a received signal in a receiving circuit, wherein said controlmeans also stops the operation of said second error amplifier dependingon said predetermined condition, said predetermined condition representssaid first signal level, and when said first signal level is lower thana predetermined value, said control means stops the operation of saidsecond error amplifier and performs such control that the output signalof said error amplifier can not be input by said third power splitter,and performs such control that the output signal of said distortionsuppression power-combiner can be output to the outside, and when saidfirst signal level is not lower than the predetermined value, saidcontrol means stops the operation of said main amplifier and performssuch control that the output signal of said error amplifier can not beinput by said distortion suppression power-combiner but can be input bysaid third power splitter, and performs such control that the outputsignal of said second distortion suppression power-combiner can beoutput to the outside.
 15. The feedforward amplifier according to claim1, further comprising: a third power splitter for splitting the outputsignal of said error amplifier into two parts; a third delay circuit fordelaying one output signal of said third power splitter; a fourth powersplitter for splitting the output signal of said distortion suppressionpower-combiner into two parts; a fourth delay circuit for delaying oneoutput signal of said fourth power splitter; a second distortiondetection power-combiner for synthesizing the output signal of saidfourth delay circuit and the other output signal of said third powersplitter; a third vector adjustor for adjusting the amplitude and phaseof the output signal of said second distortion detection power-combiner;a second error amplifier for amplifying the output signal of said thirdvector adjustor; a second distortion suppression power-combiner forsynthesizing the output signal of said third delay circuit and theoutput signal of said second error amplifier; and first signal leveldetection means of detecting a first signal level that is the signallevel of said input signal, or the signal level of a baseband signal ina baseband signal generating portion, or the signal of a transmittingsignal in a transmitting circuit, wherein said control means also stopsthe operation of said second error amplifier depending on saidpredetermined condition, said predetermined condition represents saidfirst signal level, and when said first signal level is higher than apredetermined value, said control means stops the operation of saidsecond error amplifier and performs such control that the output signalof said error amplifier can not be input by said third power splitter,and performs such control that the output signal of said distortionsuppression power-combiner can be output to the outside, and when saidfirst signal level is not higher than the first predetermined value andhigher than a second predetermined value that is smaller than said firstpredetermined value, said control means stops the operation of said mainamplifier and performs such control that the output signal of said erroramplifier can not be input by said distortion suppression power-combinerbut can be input by said third power splitter, and performs such controlthat the output signal of said second distortion suppressionpower-combiner can be output to the outside, and when said first signallevel is not higher than the second predetermined value, said controlmeans stops the operation of said error amplifier and stops theoperation of said second error amplifier, and performs such control thatthe output signal of said distortion suppression power-combiner can beoutput to the outside.
 16. The feedforward amplifier according to claim1, further comprising: a third power splitter for splitting the outputsignal of said error amplifier into two parts; a third delay circuit fordelaying one output signal of said third power splitter; a fourth powersplitter for splitting the output signal of said distortion suppressionpower-combiner into two parts; a fourth delay circuit for delaying oneoutput signal of said fourth power splitter; a second distortiondetection power-combiner for synthesizing the output signal of saidfourth delay circuit and the other output signal of said third powersplitter; a third vector adjustor for adjusting the amplitude and phaseof the output signal of said second distortion detection power-combiner;a second error amplifier for amplifying the output signal of said thirdvector adjustor; a second distortion suppression power-combiner forsynthesizing the output signal of said third delay circuit and theoutput signal of said second error amplifier; and first signal leveldetection means of detecting a first signal level that is the signallevel of a received signal in a receiving circuit, wherein said controlmeans also stops the operation of said second error amplifier dependingon said predetermined condition, said predetermined condition representssaid first signal level, and when said first signal level is lower thana second predetermined value, said control means stops the operation ofsaid second error amplifier and performs such control that the outputsignal of said error amplifier can not be input by said third powersplitter, and performs such control that the output signal of saiddistortion suppression power-combiner can be output to the outside, andwhen said first signal level is not higher than a first predeterminedvalue that is larger than said second predetermined value and higherthan said second predetermined value, said control means stops theoperation of said main amplifier and performs such control that theoutput signal of said error amplifier can not be input by saiddistortion suppression power-combiner but can be input by said thirdpower splitter, and performs such control that the output signal of saidsecond distortion suppression power-combiner can be output to theoutside, and when said first signal level is not lower than the firstpredetermined value, said control means stops the operation of saiderror amplifier and stops the operation of said second error amplifier,and performs such control that the output signal of said distortionsuppression power-combiner can be output to the outside.
 17. Thefeedforward amplifier according to any one of claims 2, 4, 5, 11, 13,and 15, wherein said first signal level detection means is provided inan upstream stage of said first power splitter, or between said firstpower splitter and said first vector adjustor, or between said firstvector adjustor and said main amplifier, or between said first powersplitter and said first delay circuit, or between said first delaycircuit and said distortion detection power-combiner, or at the input ofsaid baseband signal generating portion, or at the output of saidbaseband signal generating portion, or in said baseband signalgenerating potion, or at the input of said transmitting circuit, or atthe output of said transmitting circuit, or in said transmittingcircuit.
 18. The feedback amplifier according to any one of claims 3, 4,6, 12, 14, and 16, wherein said first signal level detection means isprovided at the input of said receiving circuit, or at the output ofsaid receiving circuit, or in said receiving circuit.
 19. Thefeedforward amplifier according to claim 4, wherein said second signallevel detection means is provided in a downstream stage of saiddistortion suppression power-combiner, or between said second powersplitter and said second delay circuit, or between said second delaycircuit and said distortion suppression power-combiner.
 20. Thefeedforward amplifier according to claim 17, wherein said first signallevel is the signal level of said input signal, and when said firstsignal level detection means detects the signal level of said inputsignal, said first signal level detection means has a signal leveldetection power-splitter for splitting said input signal into two partsand detection means of detecting said signal level of one output signalof said signal level detection power-splitter, and the other outputsignal of said signal level detection power splitter is supplied to adownstream stage.
 21. The feedforward amplifier according to claim 19,wherein said second signal level detection means has a signal leveldetection power-splitter for splitting said output signal into two partsand detection means of detecting said signal level of one output signalof said signal level detection power-splitter, and the other outputsignal of said signal level detection power-splitter is supplied to adownstream stage.
 22. The feedforward amplifier according to any one ofclaims 2, 3, 11, 12, 15, and 16, wherein the stopping of the operationof said error amplifier is to perform such control that the power supplyfor said error amplifier can be turned off and/or to perform suchcontrol that the output signal of said second vector adjustor can not beinput by said error amplifier.
 23. The feedforward amplifier accordingto any one of claims 4, 5, 6, 11, 12, 13, 14, 15, and 16, wherein thestopping of the operation of said main amplifier is to perform suchcontrol that the power supply for said main amplifier can be turned offand/or to perform such control that the output signal of said firstvector adjustor can not be input by said main amplifier.
 24. Thefeedforward amplifier according to any one of claims 13, 14, 15, and 16,wherein the stopping of the operation of said second error amplifier isto perform such control that the power supply for said second erroramplifier can be turned off and/or to perform such control that theoutput signal of said third vector adjustor can not be input by saidsecondary error amplifier.
 25. A communication equipment comprising: abaseband generating portion for generating a baseband signal; and atransmitting circuit for outputting a transmitting signal from saidbaseband signal generated, wherein the feedforward amplifier accordingto any one of claims 1 to 6, 11 to 16, 19, and 21 is used for saidtransmitting circuit.